>84 



COMPOSITAE. 



[Vol,. III. 



34. MACHAERANTHERA Nees, Gen. & Sp. Ast. 224. 1832. 



Annual, biennial or perennial branched herbs, with leaf)' stems, alternate, mostly serrate or 

 pinnatifid leaves, the teeth or lobes usually bristle-tipped, and large heads of both tubular and 

 radiate flowers. Involucre of numerous series of imbricated canescent or glandular bracts 

 with herbaceous or foliaceous spreading or appressed tips. Receptacle alveolate, the alveoli 

 usually toothed or lacerate. Ray-flowers numerous, violet to red or purple, pistillate. Disk 

 flowers perfect, their corollas tubular, 5-lobed, yellow, changing to red or brown; anthers 

 exserted, appendaged at the tip, rounded at the base; style-appendages subulate to lanceo- 

 late. Achenes turbinate, narrowed below, pubescent. Pappus of numerous stiff rough un- 

 equal bristles. [Greek, sickle-anther.] 



About 15 species, natives of western North America. 

 Annual or biennial; leaves pinnatifid. i. M. tanaceti folia. 



Perennial or biennial; leaves sharply serrate. 2. M. sessiliflora. 



i. Machaeranthera tanacetifolia (H.B.K.) Nees. Tansy Aster. 



Dagger-flower. (Fig. 3809.) 



Aster tanacetifolins H.B.K. Nov. Gen. Sp. 4:95. 1820. 

 Machaeranthera tanacetifolia Nees, Gen. & Sp. Ast. 

 225. 1832. 



Annual or biennial; stem glandular-pubescent, 

 often viscid, densely leafy, much branched and 

 bushy, i-2 high. Leaves sessile, or short-peti- 

 oled, pubescent, the lowest x'-jf long, 2-3-pinnati- 

 fid, their lobes linear or oblong, acute or mucron- 

 ate, the upper pinnatifid, those of the branches 

 sometimes entire; heads numerous, corymbose- 

 paniculate, i / -2 / broad; involucre hemispheric, 

 4 // -6 // high, its bracts linear, glandular, imbricated 

 in 5-7 series, their green tips very squarrose; rays 

 15-25, violet-purple, 5 // -S // long, pappus copious, 

 tawny; achenes villous. 



In dry soil, Nebraska to Texas and Mexico, west to 

 California. June-Aug. 



2. Machaeranthera sessiliflora (Nutt.) 

 Greene. Viscid Aster. (Fig. 3810.) 



Dieteria sessiliflora Nutt. Trans. Am. Phil. Soc. 7, 301. 



1840. 

 Machaeranthera sessiliflora Greene, Pittonia, 3: 60. 



1896. 



Stem usually stout, finely rough-pubescent or 

 canescent, branched, and viscid-glandular above, 

 i-2 high. Leaves lanceolate, linear, or the lowest 

 spatulate, sessile, somewhat viscid, sharply incised- 

 dentate, the larger i / -3 / long, the teeth bristle-tip- 

 ped; heads numerous, racemose, or corymbose above, 

 i'-i 



V,' 



broad, the lower often nearly sessile; invo- 

 lucre broadly turbinate or hemispheric, 4 // -6 // high, 

 its bracts acute, imbricated in 6-10 series, their tips 

 strongly squarrose; rays numerous, violet, 4 // -6 // 

 long; pappus copious; achenes narrow, appressed- 

 pubescent. 



In dry soil, central and western Nebraska. Has been 

 referred to Aster canescens. July-Oct. 



35. ERiGERON L. Sp. PI. 863. 1753. 

 Branching or scapose herbs, with alternate or basal leaves, and corymbose, paniculate or 

 solitary, peduncled heads, of both tubular and radiate (rarely all tubular) flowers. Involucre 

 hemispheric or campanulate, its bracts narrow, nearly equal, imbricated in but 1 or 2 series 

 in our species. Receptacle nearly flat, usually naked. Ray- flowers, in our species, white, 

 violet or purple, pistillate. Disk-flowers yellow, tubular, perfect, their corollas mostly 5- 

 lobed. Anthers obtuse and entire at the base. Style-branches more or less flattened, their 



